In general, one of multi-carriers is used as a primary carrier and the other is used as a subcarrier.
In a wireless communication system supporting multi-carriers, a base station transmits a control message to a terminal through primary carriers. That is, a traffic indication message for notifying a terminal that has entered a sleep window of whether there are data that will be transmitted by a base station is transmitted to the terminal from the base station through the primary carrier.
However, when primary carriers used by a plurality of terminals that have entered the sleep window are different, the base station has to transmit the traffic indication message by using the primary carriers used by the respective terminals, and hence the radio resource is inefficiently used. Also, the base station increases a load according to transmission of the traffic indication message.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.